Investigation On Preparing MAPbI₃ And FA_0.2MA_0.8PbI₃ Single-crystal-like Films By Anti-solvent Thermal-pressed Method And The Properties Of Photodetectors

Because of the superior photoelectric properties which are comparable with inorganic semiconductors,including high optical absorption coefficient,adjustable energy gap,low exciton binding energy and long carrier diffusion length etc.,organic-inorganic hybrid perovskite semiconductors materials have been extensively applied in the fabrication of thin-film optoelectronic devices.Herein,the crystallization quality of the organic-inorganic hybrid perovskite films is the key factor that dominating the performance of these devices.Thus,preparing organic-inorganic hybrid perovskite films with large crystal size,high crystallinity,low defect density and high surface coverage is the most effective route to strikingly improve the performance of the devices.In order to achieve this goal,proposed the anti-solvent thermal-pressed method,through develop high-pressure drive ion diffusion engineering based on the traditional anti-solvent method,by using pressure driven grain boundary fusion and grain secondary growth in the film,high-quality MAPbI3 and low defect density,uniaxial oriented FA0.2MA0.8PbI3 single-crystal-like films were obtained,and high-performance photodetector devices were developed with high-quality perovskite films.The main research content of the thesis included:(1)A uniformly dense MAPbI3 precursor polycrystalline film was prepared by traditional anti-solvent method,and then the polycrystalline film was treated under high static pressure.Through the system optimization of thermal-pressure treatment conditions:temperature,pressure,time and temperature ramping speed and other parameters,determine the optimal treatment conditions(150℃,150 MPa),achieve the effective growth of the film,got MAPbI3 single-crystal-like film with the grain size increase,long carrier life,low defect density and improved environmental stability,high surface coverage and vertical substrate direction to achieve single crystal penetration.The photoelectric properties of the photodetectors prepared by the MAPbI3 single-crystal-like film as the active layer were improved,the responsivity was 282.9 mA W-1(671 nm,3.4×10-3 mW cm-1),the detectivity was 8.6×1013 Jones(671 nm,3.4×10-3 mW cm-2),and the On/Off ratio was as high as 3×105(671 nm,100 mW).(2)Based on the anti-solvent thermal-pressed method,a "mild" high-pressure drive ion diffusion engineering(100℃,75 MPa)was developed.Based on the SnO2/ITO substrate,a uniaxial oriented FA0.2MA0.8PbI3 film with low defect density,long carrier life and high stability composed of large size grains was prepared,and the single crystal surface and vertical direction of single crystal penetration were realized,which significantly promoted the transport and separation of carriers.Device performance has been significantly improved,and SPPD based on Perov-HPID75 thin films exhibit high responsivity and good environmental stability.At 671 nm laser irradiation of a bias of 0 V,when laser intensity is 3.4×10-3 mW cm-2,the responsivity is 512 mA W-1,and the detectivity is 1.4×1012 Jones.Even if the thickness of the Perov-HPID75 film is less than 200 nm or higher than 1 μm,the responsivity were over 185 mA W-1.Without any packaging,the photocurrent photocurrent drops by only 7.5%after 15 days in an environment with a humidity of 20%to 30%.